Control valve mechanism



April 1941- M. N. STADLIN 2,239,657

7 common v'Am/E' MECHANISM Filed Oct. 29, 1937 Low PEEasuaE Q 2! 22 g l2 Damn INVENTOR MYEB N. STADLIN Patented Apr. 22, 1941 UNITED STATES PATENT OFFICE CONTROL VALVE MECHANISM Myer N. Stadlin, Philadelphia, Pa., assignor, by mesne assignments, to The Baldwin Locomotive Works, a corporation of Pennsylvania Application October 29, 1937, Serial No. 171,773

2 Claims; 137-53) This invention relates to an improved control valve mechanism and more particularly to an improved drain valve mechanism that is adapted for by-passing a low pressure pump when a predetermined pressure is built up in a hydraulic system and for thereupon causing a high pressure pump to supply the system.

The present invention is especially useful in hydraulic press control systems involving rela tively high operating unit pressures. In such press systems a platen is ordinarily initially moved into engagement with the work pieceunder a large volume of fluid of relatively low pressure or the platen moves toward the work piece under gravity after which the low pressure fluid is initially applied to the workpiece. After such initial movements in either case, the final pressing stroke of the platen is efiected by a relatively small volume of fluid of very high pressure. It is generally more economical to employ one pump for producing the small pressure and a separate pump for producing the high pressure. Various combination by-pass and check valves have heretofore been proposed and used for automatically cutting out the low pressure pump upon occurrence of a predetermined pressure whereupon the high pressure pump then constitutes the sole source of operating fluid for the press. These prior art systems have involved certain deficiencies such as the use of excessively large controlling springs with consequent lack of sensitivity in changing over at the desired predetermined pressure or in adjusting thesame.

It is an object of my invention to provide an improved control valve mechanism of the foregoing type that will have a high degree of sensitivity. A further object is to provide such an improved control valve mechanism that will permit smaller control and operating springs tobe employed, thereby facilitating the accomplishment of sensitivity. It is a further object of my invention to provide an improved control valve so constructed and arranged as to be economical in initial cost, operation and maintenance while at the same time being relatively simple in construction and operation whereby the various parts are readily accessible for inspection, repair or adjustment but without in any way sacrificing the desired degree of sensitivity of my improved control mechanism.

Other objects andadvantages will be more apparent to those skilled in the art from the following description of the accompanying drawing in which:

Fig.1 is an enlarged sectional view of the con- ,trol valve mechanism taken on the line 'l l of Fig. 2;

Fig. 2 is a sectional view taken on the of Fig. 1.

In the particular embodiment of the invention, such as is disclosed herein merely for the purpose of illustrating one specific form among possible others that the invention might take in practice, my improved control mechanism comprises as shown in Figs. 1 and 2 a casing 8 provided with a low pressure inlet 9 and a low pressure chamber l0 while a high pressure inlet ll connects with a normally high pressure chamber I2 whichin turn is connected by a pipe l3 to a hydraulic system such as hydraulic press controls. Low and high pressure chambers l0 and I2 are also adapt ed to communicate with each other through a vertical passageway l4 normally closed by a spring pressed check valve l5 which in turn is provided with an equalizing pressurefluid passageway IS. A by-pass drain I! is adapted to be brought into communication with low pressure chamber l0 when a by-pass drain valve I8 is open, the by-pass drain valve being opened when a preline 22 determined pressure is reached in chamber H) at which time check valve [5. closes. Thereupon only high pressure is supplied through inlet II to the hydraulic system outlet l3.

By-pass drain valve l8 has a cylinder 2!) and a piston 2| formed as part of the Valve I8. The under side of piston 2! is, as shown in Fig. 1, exposed to the fluid in chamber l2 while the top side of piston 2| is exposed to fluid in chamber l0 through a lateral pipe connection 22, Fig. 2. This pipe connection extends fromthe chamber ID to a passageway 23 in a combined pilot valve casing and cylinder'head 24 and'thence downwardly through a passageway 25. The valve [8 is biased towards its closing position by a spring 26.

To efiect opening of the valve l8 in a manner to be shortly described, a pilot valve in the nature of an adjustable spring pressed ball valve 26a, is' adapted to allow passage 23 to communicate with a vertical passage 21 and thence to a chamber 28 which receives the upper end of the valve l8. A suitable screw 30 is adapted to adjust the spring force on ball valve 26a.

vOperation.Assuming that the hydraulic system is to be initially operated under low pressure, fluid pressure .from suitable low and high pres-. sure sources such as pumps (not shown) will be supplied simultaneously to inlets 9 and H respectively, although the system pressure in pipe l3 cannot build up above a certain minimum value until suflicient resistance in the system builds up. In the case of a hydraulic press, the fore' going minimum pressure occurs during the initial work stroke or movement of a press platen. During this operation drain valve I8 is closed and check valve l5 will open by reason of the low pressure pump circulating a larger volume of fluid than does the high pressure pump through inlet I I whereby the low pressure fluid in chamher flows upwardly through passage M to raise check valve I5. increases, the pressure in chambers l0 and I2 will gradually increase until a predetermined minimum pressure of say 450 pounds per square inch is obtained. During this increase of pressure which is present in both chambers If) and I2 and also beneath piston 2|, Fig. l, valve I8 is held to its seat by reason of the pressures on the top and bottom of piston 2| being equal, thereby allowing spring 26 to exert the principal closing force on the valve. The foregoing equalization of fluid pressures is obtained because low: pressure chamber Ill is in communication with the top side of piston 2| through passages 22, 23 and 25. When a predetermined minimum pressure is obtained in chambers ill and I2 as above mentioned, ball valve 25a, Fig. 2, opens, thereby connecting the upper end of cylinder 20 through passages 25, 23 and 21 to the interior 28 of valve I8 and thence with a passage 32 leading to drain l1. By reason of passages 25, 21 and 32 being relatively large compared to a very restricted passageway in pipe connection 22, the pressure on the top side of piston 21 is relieved sufliciently so that the pressure in chamber l2 acting on the under side of piston 2| will raise valve I 8 and allow unrestricted flow of pump fluid from low pressure inlet to drain I1. Simultaneously with the relief of pressure in chamber In, check valve l5 automatically closes by virtue of pressure in chamber l2 being communicated through passage 5 to the upper side of check valve l5 whereupon the spring 34 causes closure of the check valve. As a result of the foregoing opening of the valve l8 and closure of check valve IS, the supply of low pressure is eflectively disconnected from the hydraulic system so that thereafter high pressure fluid is the sole source of fluid supply for the system. As the system resistance builds up due to increasing force required to move say a press platen against the work piece, the high pressure pump will generate the increasing pressure. This increasing pressure will continuously bear on the under side of piston 2| to hold the valve l8 open. After the valve 18 has opened so that the interior thereof isin communication with atmosphere through passage 32 and drain l1, ball valve 260. closes, but regardless of any minimum pressure that may accumulate in the upper end of cylinder 20, the increasingly high pressure in chamber I2 will positively hold valve l8 open.

When the system pressure dropsbelow a predetermined value, spring 26 will ultimately be As the system resistance I sufficient to close valve 18 against the pressure in chamber 12 whereupon the low pressure pump 3 will supply its relatively large volume low pressure fluid to chamber Ill and accordingly open check valve 15 so that the low pressure supply is again in communication with the hydraulic system through pipe l3. As the pressure in cham-: ber l0 increases it will gradually increase in passages 23 and 25 and this increasing pressure will act on the upper side of piston 21 until a predetermined pressure is reached to open ball valve 260. to again repeat a high pressure operation as already described.

From the foregoing disclosure it is seen that I have provided a control valve mechanism suitable for dual pressure sources of supply for sequentially connecting the low pressure source and the high pressiu'e source respectively to a hydraulic system, all with a control valve mechanism that has a high degree of sensitivity for effecting the changeover from low to high pressure and which involves relatively light operat ing and control springs but without in any way sacrificing the positiveness or dispatch of operation. Also the structure for accomplishing the foregoing is not only economical in construction, operation and maintenance but is also arranged so as to have maximum convenience in accessibility of the parts for inspection or repair. The predetermined pressure at which the hydraulic system is changed over from low to high pressure can be readily adjusted merely by adjusting screw 30 whereby the responsiveness of pilot valve 260. is varied accordingly.

It will of course be understood that various changes in details of construction and arrangement of parts may be made bythose skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. A drain valve mechanism comprising, in combination, a casing having a fluid chamber provided with a supply inlet and a main outlet and a drain outlet for supplied fluid, a valve for closing said drain outlet, a spring normally biasing said valve to its closed position, a vaive operating piston and a cylinder therefor having heads at each end thereof to provide opening and closing chambers'each separate from said fluid chamber, means for supplying pressure present in said chamber to the opening end of said cylinder, means for supplying operating fluid to the opening end of said cylinder independently of the fluid chamber, means for supplying operating fluid from said fluid chamber to the closin end of said cylinder and for exhausting fluid from said closing end, said latter means including two communicating passages of different cross-sectional area the smaller one of which communicates with said fluid chamber and the larger one of which communicates with said closing end of the cylinder and also an exhaust port communicating directly with said passage of larger cross-sectional area, said exhaust port being of larger cross-sectional area than said smaller passage, and a spring pressed valve for normally closing said port, whereby said spring pressed valve opens in response to a predetermined pressure in said fluid chamber thereby to relieve pressure in the closing end of said cylinder and allow the by-pass valve to open and re main open under the influence of fluid pressure in the opening end of said cylinder.

2. The combination set forth in claim 1 further characterized in that an exhaust passage also of larger cross-sectional area than said smaller passage is provided axially through said valve which closes said drain outlet, and said exhaust port communicates with said axial passage.

- MYER N. STADLIN. 

